An analog-to-digital converter (ADC) is a device that converts an analog quantity into a discrete digital value. Typically, an ADC is an electronic device that converts an input analog voltage (or current) to a digital value proportional to the magnitude of the voltage or current.
A large number of ADCs have been proposed for converting analog signals into digital signals. Some example types of ADCs include a direct conversion, successive approximation, ramp-comparison, dual- or multi-slope, delta-encoding, pipeline, and time-interleaving ADCs.
Since a large number of ADCs exist the ADC implementations can vary in a number of ways. For example, the implementations can vary in differing usages of passive (e.g., resistors, capacitors) and active (e.g., diodes, transistors) elements. While existing ADCs have been successful in many applications, size, cost, manufacturing, and integration issues of the ADCs can be prohibitive in implementing ADC functionality in modern electronic devices and systems.